Add quick fix to remove single lambda parameter if it's unused #KT-14593 Fixed

idea/src/org/jetbrains/kotlin/idea/quickfix/QuickFixRegistrar.kt

@@ -277,6 +277,7 @@ class QuickFixRegistrar : QuickFixContributor {
         NO_VALUE_FOR_PARAMETER.registerFactory(ChangeFunctionSignatureFix)
         UNUSED_PARAMETER.registerFactory(RemoveUnusedFunctionParameterFix)
         UNUSED_PARAMETER.registerFactory(RenameToUnderscoreFix.Factory)
+        UNUSED_PARAMETER.registerFactory(RemoveSingleLambdaParameterFix)
         EXPECTED_PARAMETERS_NUMBER_MISMATCH.registerFactory(ChangeFunctionLiteralSignatureFix)
 
         EXPECTED_PARAMETER_TYPE_MISMATCH.registerFactory(ChangeTypeFix)

idea/src/org/jetbrains/kotlin/idea/quickfix/RemoveSingleLambdaParameterFix.kt

@@ -0,0 +1,54 @@
+/*
+ * Copyright 2010-2016 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.jetbrains.kotlin.idea.quickfix
+
+import com.intellij.codeInsight.intention.IntentionAction
+import com.intellij.openapi.editor.Editor
+import com.intellij.openapi.project.Project
+import org.jetbrains.kotlin.diagnostics.Diagnostic
+import org.jetbrains.kotlin.lexer.KtTokens
+import org.jetbrains.kotlin.psi.KtFile
+import org.jetbrains.kotlin.psi.KtLambdaExpression
+import org.jetbrains.kotlin.psi.KtParameter
+import org.jetbrains.kotlin.psi.KtParameterList
+
+class RemoveSingleLambdaParameterFix(element: KtParameter) : KotlinQuickFixAction<KtParameter>(element) {
+    override fun getFamilyName() = "Remove single lambda parameter declaration"
+    override fun getText() = familyName
+
+    override fun invoke(project: Project, editor: Editor?, file: KtFile) {
+        val parameterList = element.parent as? KtParameterList ?: return
+        val ownerFunction = parameterList.ownerFunction ?: return
+        val arrow = ownerFunction.node.findChildByType(KtTokens.ARROW) ?: return
+
+        parameterList.delete()
+        ownerFunction.node.removeChild(arrow)
+    }
+
+    companion object : KotlinSingleIntentionActionFactory() {
+        override fun createAction(diagnostic: Diagnostic): IntentionAction? {
+            val parameter = diagnostic.psiElement as? KtParameter ?: return null
+            val parameterList = parameter.parent as? KtParameterList ?: return null
+
+            if (parameterList.parameters.size != 1) return null
+
+            if (parameterList.parent?.parent !is KtLambdaExpression) return null
+
+            return RemoveSingleLambdaParameterFix(parameter)
+        }
+    }
+}

idea/testData/quickfix/removeSingleLambdaParameter/multiple.kt

@@ -0,0 +1,10 @@
+// "Remove single lambda parameter declaration" "false"
+// ACTION: Move lambda argument into parentheses
+// ACTION: Rename to _
+// ACTION: Specify explicit lambda signature
+// ACTION: Specify type explicitly
+// WITH_RUNTIME
+
+fun main() {
+    mapOf(1 to 2).forEach { t, <caret>u -> println(t) }
+}

idea/testData/quickfix/removeSingleLambdaParameter/simple.kt

@@ -0,0 +1,6 @@
+// "Remove single lambda parameter declaration" "true"
+// WITH_RUNTIME
+
+fun main() {
+    listOf(1).forEach { <caret>x -> println() }
+}

idea/testData/quickfix/removeSingleLambdaParameter/simple.kt.after

@@ -0,0 +1,6 @@
+// "Remove single lambda parameter declaration" "true"
+// WITH_RUNTIME
+
+fun main() {
+    listOf(1).forEach { <caret>println() }
+}

idea/tests/org/jetbrains/kotlin/idea/quickfix/QuickFixTestGenerated.java

@@ -7272,6 +7272,27 @@ public class QuickFixTestGenerated extends AbstractQuickFixTest {
         }
     }
 
+    @TestMetadata("idea/testData/quickfix/removeSingleLambdaParameter")
+    @TestDataPath("$PROJECT_ROOT")
+    @RunWith(JUnit3RunnerWithInners.class)
+    public static class RemoveSingleLambdaParameter extends AbstractQuickFixTest {
+        public void testAllFilesPresentInRemoveSingleLambdaParameter() throws Exception {
+            KotlinTestUtils.assertAllTestsPresentByMetadata(this.getClass(), new File("idea/testData/quickfix/removeSingleLambdaParameter"), Pattern.compile("^([\\w\\-_]+)\\.kt$"), true);
+        }
+
+        @TestMetadata("multiple.kt")
+        public void testMultiple() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/removeSingleLambdaParameter/multiple.kt");
+            doTest(fileName);
+        }
+
+        @TestMetadata("simple.kt")
+        public void testSimple() throws Exception {
+            String fileName = KotlinTestUtils.navigationMetadata("idea/testData/quickfix/removeSingleLambdaParameter/simple.kt");
+            doTest(fileName);
+        }
+    }
+
     @TestMetadata("idea/testData/quickfix/removeToStringInStringTemplate")
     @TestDataPath("$PROJECT_ROOT")
     @RunWith(JUnit3RunnerWithInners.class)